Unfiltered air inleakage analysis of the control room envelope of Kuosheng nuclear power plant

Abstract The control room envelope (CRE) of a nuclear power plant is quite important during all kinds of the accidents. Only with the guaranteed habitability of the CRE, the operators can shut down the reactor safely during an accident with the release of hazardous chemicals or radioactive gases. In this study, Kuosheng nuclear power plant (NPP) in Taiwan had performed the inleakage test by using tracer gas technique, and six cases with different heating, ventilation and air conditioning system (HVAC) lineups were tested in this study. The test results showed that the unfiltered inleakage rate for the pressurization modes ranged from 0.063 m3/s to 0.098 m3/s and were all within the acceptance criteria of 0.212 m3/s. For the isolation modes, the unfiltered inleakage rate ranged from 0.240 m3/s to 0.321 m3/s and were still within the acceptance criteria of 0.944 m3/s. The test result provided useful information to improve the vulnerability of the CRE. It also showed that a decrease in the positive differential pressure of the CRE relative to its surroundings did not inevitably increase the unfiltered inleakage rate of the CRE if the critical boundary, such as the negative differential portions of the ventilation system, were still well sealed.